<p>Background Oral squamous cell carcinoma (OSCC) is a common malignant tumor of the oral cavity with a poor prognosis. Purpose This study aimed to investigate the expression, biological functions, and clinical significance of miR-135b-5p in OSCC. Methods Bioinformatic analysis was used to predict targets of miR-135b-5p, and a dual-luciferase reporter assay verified the targeting relationship with TXNIP. In OSCC cell lines, cell proliferation and migration were assessed using CCK-8 and Transwell assays, respectively; oxidative damage and ferroptosis were evaluated by detecting intracellular levels of Fe²⁺, ROS, MDA, SOD, and related molecular markers. Additionally, peripheral blood samples from 117 OSCC patients were collected to analyze the correlation between miR-135b-5p and TXNIP expression and their relationship with clinicopathological parameters and patient prognosis. Results MiR-135b-5p was significantly upregulated in OSCC cells and patient blood, while TXNIP was downregulated. Overexpression of miR-135b-5p promoted OSCC cell proliferation and migration. Inhibition had the opposite effects. The dual-luciferase reporter assay confirmed that miR-135b-5p directly targets and negatively regulates TXNIP. Inhibition of miR-135b-5p or overexpression of TXNIP induced oxidative damage and promoted ferroptosis. Conversely, miR-135b-5p overexpression reduced H₂O₂-induced ferroptosis—an effect reversed by concurrent TXNIP overexpression. Clinical analysis revealed a significant negative correlation between miR-135b-5p and TXNIP expression. High miR-135b-5p expression or low TXNIP expression was significantly associated with lymph node metastasis and poorer overall survival. Multivariate Cox regression analysis indicated that both were independent prognostic factors for OSCC. Conclusion The miR-135b-5p/TXNIP axis critically regulates OSCC progression through ferroptosis and may serve as a prognostic biomarker and therapeutic target for OSCC.</p>